Carboxyl containing polymers of vinyl or vinylidene monomers containing at least one terminal CH.sub.2 .dbd.C&lt; group are well known. Such polymers may be homopolymers, or copolymers with other vinyl or vinylidene monomers and unsaturated polymerizable carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid and the like. Often copolymers of these acids are cross-linked with small amounts of cross-linking agents. These materials are normally prepared by polymerization with a free radical catalyst in an organic medium in a closed vessel or autoclave equipped with stirring. During the course of such polymerizations, polymer begins to precipitate from the solution as it is formed and flocculates and forms aggregates. This aggregation is generally uncontrolled and interferes with the polymerization reaction by retarding access of monomer to free radicals and contributing to poor removal of the heat produced by the polymerization. As a consequence, it is difficult to obtain uniform polymerizations because of the variation in temperature and the aggregation of polymers. This effect often becomes worse when there is local variation in temperature in different reactor regions. Consequently, variation of product quality from lot to lot is obtained. Further, the precipitated polymer forms a slurry in the solvent which becomes extremely thick; this results in ineffective mixing, and generally causes extensive fouling on reactor surfaces. A further problemm is that solvent and monomers are trapped in the polymers during aggregation and removal of such trapped solvent is time consuming, decreases production rates and makes it difficult to obtain dried carboxyl containing products having less than 500 ppm of residual media in the polymer product.
U.S. Pat. No. 4,375,533 to Park et al. disclosed a process for overcoming some of the above problems. The Park et al. process for the polymerization of acrylic acid and optional comonomers in an organic media is characterized by the use of nonionic surface active agents having HLB values between 1 and about 10.
Similarly, U.S. Pat. No. 4,419,502 to Sehm, disclosed a process for the polymerization of acrylic acid and optional comonomers in the presence of a nonionic surface active agent selected from polyoxyethylene alkyl ethers and polyoxyethylene sorbitol esters and having an HLB value greater than 12 l and U.S. Pat. No. 4,420,596 to Lochhead et al. disclosed a process for polymerizing carboxylic acids in mineral spirits. This process also employed nonionic surface active agents having HLB values less than 10.
Lastly, U.S. Pat. No. 4,526,937 to Hsu teaches the polymerization of acrylic acid in an organic solvent with a free radical catalyst. This process incorporates nonionic block copolymers of propylene oxide and ethylene oxide to minimize undesirable flocculation and agglomeration.
An object of the instant invention is to develop an improved process for the polymerization of acrylic acid and various comonomers by employing oil soluble ionic surface active agents in the polymerization process. It is an object of the instant invention to reduce build up and obtain more satisfactory particle sizes for the precipitated polymer, which will result in better heat transfer and higher total solids produced.